1. Field of the Invention
The present invention relates to a control technique for transferring data read from a storage medium to a temporary storage unit, and typically relates to a technique applied to a reproducing apparatus that reads data from various types of storage media, such as Blu-ray Disc (BD), digital video disc (DVD), compact disc (CD) and memory card, and transfers the data to a temporary storage unit in reproduction processing.
2. Description of the Related Art
A reproducing apparatus that reads data stored in a storage medium and reproduces the data is widely used for reproducing music or video.
For example, a reproducing apparatus that reproduces video, such as a movie stored in a DVD, a reproducing apparatus that reproduces a music stored in a CD, and a reproducing apparatus that supports various types of storage media, such as DVD and CD, and reproduces a music, a movie or the like stored in the storage media are widely known.
Such a reproducing apparatus, reading a large amount of digital data, such as a music or movie, from a storage medium and performing reproduction processing, including decoding, on the digital data, needs to overcome noise generated due to high-frequency driving of a reading means for reading digital data (e.g., an optical pickup) and a noise generated due to processing of digital data as high frequency signal.
In order to overcome noise generated when data is read from a storage medium, an optical disc apparatus has been proposed that shields radiated emission of high frequency signal generated due to driving of an optical pickup housed in a DVD unit, by magnetically shielding the radiated emission of high frequency signal at a portion of the front and bottom surfaces and a portion of the both sides and rear surfaces of the DVD unit (JP-A-2002-140887).
In order to overcome noise generated due to internal processing of an apparatus, a DVD apparatus has been proposed that significantly reduces radiated emission by, in a configuration in which a circuit board is divided into a digital circuit board and a power supply board that are placed on both sides of an optical disc loader, changing how to divide the ground pattern of the digital circuit board and placing a filter on the digital circuit board adjacent to a connector (JP-A-2005-18849).
In order to overcome a problem in which, when a control signal, such as a tracking error signal output from an optical pickup, includes noise due to a high frequency component, a tracking servo control unit receiving the amplified control signal becomes unstable in position control of the optical pickup, an optical disc apparatus has been proposed that determines the type (application, country of manufacture, manufacturer and the like) of an optical medium applied to the optical disc apparatus, and, when the optical medium is a specified optical medium, activates a frequency characteristic change circuit to change the frequency characteristic to be applied to a control signal input to a servo IC so that the high frequency component of the control signal will be attenuated, thereby reducing high frequency noise included in the control signal (JP-A-2000-67441).
In order to provide an information recording/reproducing apparatus that can record/reproduce information to/from plural types of recording media without increasing the amount of hardware, an information recording/reproducing apparatus has been proposed that determines the type of a loaded optical disc (e.g., DVD or BD or the like) and changes the configuration of plural logic circuits in a reconfigurable circuit according to a program corresponding to the type of the optical disc to configure a modulation/demodulation circuit and an error correction circuit corresponding to the type of the optical disc, which allows configuration of a different type of the modulation/demodulation circuit and the error correction circuit depending on the various types of optical discs without increasing the amount of hardware (JP-A-2007-141310).
In order to provide an optical disc apparatus that controls any type of optical disc using the same CPU or optical disc controller and provides high performance and high reliability, an optical disc controller has been proposed that includes: a rewritable memory for storing information necessary for recording/reproducing of an optical disc; a determination unit for determining the type and sub-type of an optical disc; a search unit for searching a region in which the control information for the optical disc is recorded, based on the determination result given by the determination unit; a reproduction unit for reproducing the control information recorded in the region searched by the search unit; and a memory control unit for changing memory allocation based on at least one of the determination result and the control information reproduced by the reproduction unit (JP-A-2003-51152).
As described above, a reproducing apparatus, such as an optical disc apparatus, performs read processing of reading a large amount of data, such as a music or movie, from a storage medium and reproduction processing of reproducing the read data, in which, at present, the speed of the reproduction processing is slower than that of the read processing.
Specifically, whereas the processing of reading data from a storage medium can be quickly performed easily, the reproduction processing includes a complicated and time-consuming processing, such as data decoding, and also includes a processing of reproducing a music or movie in accordance with the speed of outputting to a speaker or display, which takes a certain amount of time.
Accordingly, the reproducing apparatus, including a temporary storage unit for temporarily storing data to be reproduced, reads data from the storage medium, then transfers and stores the data in the temporary storage unit, and then sequentially reads and reproduces the data stored in the temporary storage unit.
The present invention is made in the light of the event in which increase in the number of types of storage media that the reproducing apparatus can support causes noise also in transferring data to the temporary storage unit.
Specifically, the rate of transferring data to the temporary storage unit is previously constant, however, when the amount of data read from the storage medium is small (for example, the amount of data read from a CD is significantly smaller than that from a DVD), clusters of data are transferred to the temporary storage unit intermittently (e.g., at intervals of one second), as shown in the left of FIG. 3(a).
As a result, this intermittent transfer of data causes a large amount of current to instantaneously and repeatedly flow, thereby generating a high-intensity radio wave as noise.
However, no invention has been made to overcome the above-described problem, and no technique has existed to effectively manage noise due to transferring data to the temporary storage unit.
As a common practice, one method may be to cover a noise-generating portion with a shield plate. However, this method increases the number of parts, leading to a larger apparatus, a more complicated structure, and a higher product cost, so this method is not an effective solution.
In view of the above problem, it is an object of the present invention to provide a reproducing apparatus that suppresses or prevents noise generation in transferring data to a temporary storage unit.